The invention disclosed herein was made with Government support under the NSF Grant No. CHE98-02316. Accordingly, the U.S. Government has certain rights in this invention.
Throughout this application, various references are referred to within parentheses. Disclosures of these publications in their entireties are hereby incorporated by reference into this application to more fully describe the state of the art to which this invention pertains. Full bibliographic citation for these references may be found at the end this application, preceding the claims.
Nonracemic columnar liquid crystalline materials have been widely used in display devices such as those in calculators, digital watches, flat panel computer screens and flat penal televisions. Most of these nonracemic columnar liquid crystalline materials include planar discotic mesogens in which the asymmetry is in the side chains.1-12 The only examples in which the cores are chiral are derivatives of saccharides,13-14 inositols,13-15 and cyclotriveratrylene.16 Remarkably, no property of any of these latter materials"" mesophases has yet been detected that is consequent on the cores"" chirality. In their review in 1992,14 Jeffrey and Wingert asserted that to their knowledge xe2x80x9cthere is no basic distinction between the mesophases formed by derivatives of a chiral molecule, such as D-glucitol, and a meso molecule, such as galactitol.xe2x80x9d This distinction appears not to have been made in the few years since that review.
While attempts have been made to synthesize mesogenic materials in which the planar aromatic cores of molecules constituting liquid crystals are twisted helically,17-19 in part because chiral columnar liquid crystals have the capacity to undergo ferroelectric switching,1,2,5,20 none that is nonracemic has been obtained until now. We describe below the synthesis and uses of the first, nonracemic helical columnar liquid crystal and its applications in making a helical discotic switch.
The present invention provides a helicene compound having the structure: 
wherein X is O, or S and Y is xe2x80x94Oxe2x80x94C(xe2x95x90O)CH2xe2x80x94Oxe2x80x94R5, wherein R5 is H, substituted or unsubstituted alkyl, alkenyl, cycloalkyl, aryl, or arylalkyl, wherein R1, R2, R3 and R4 are independently the same or different and are substituted or unsubstituted alkyl, alkenyl, cycloalkyl, aryl, or arylalkyl.
The present invention further provides a helicene compound wherein R1, R2, R3 and R4 are substituted or unsubstituted alkyl or aryl.
The present invention also provides liquid crystal having a spiral coil structure and a dipole moment along its axis, comprising a helicene compound having the structure: 
wherein X is O, or S and Y is xe2x80x94Oxe2x80x94C(xe2x95x90O)CH2xe2x80x94Oxe2x80x94R5, wherein R5 is H, substituted or unsubstituted alkyl, alkenyl, cycloalkyl, aryl, or arylalkyl, wherein R1, R2, R3 and R4 are independently the same or different and are substituted or unsubstituted alkyl, alkenyl, cycloalkyl, aryl, or arylalkyl; wherein the liquid crystal has the capacity to undergo ferroelectric switching.
The invention also provides a helical discotic switch comprising (a) the liquid crystal, (b) a rubbed substrate deposited with the liquid crystal having a planar orientation, and (c) electrodes for applying an electric field perpendicular to the rubbed substrate which changes the orientation of the liquid crystal, thus preventing the transmission of light.